The use of DC arc optical emission spectroscopy (OES) for quantitative analysis of thin films deposited on graphite electrodes was investigated as a process control tool. Three binary systems were evaluated: nickel-chromium, phosphorous-silicon, and silicon-aluminum. Sampling by direct deposition onto graphite electrodes placed in the deposition chamber with product runs proved to be a rapid, representative, and non-disruptive technique. Standard electrodes were prepared for each system either by evaporation of solutions of known concentration onto the tips of electrodes or by weighing out powdered standards of the appropriate concentrations. Standard curves were then prepared by burning multiple sets of standard electrodes in a DC arc of 15 amperes and obtaining intensity rations of selected analytical line pairs. Comparison of the OES technique with atomic absorption, electron microprobe, or gravimetric analysis of samples from the same deposition showed absolute agreement to within ±3% for the nickel-chromium system, ±0.3% for the phosphorous-silicon system, and ±0.2% for the silicon-aluminum system. Maximum relative percent error for the techniques were 5%, 10%, and 12.5% respectively.

<p>Nanocomposite thin films are materials that have the potential to improve and tune many properties for various applications in electronics, sensors, memory storage, and optics. Materials properties are a consequence of their structure, so being able to manipulate the nanostructure of nanocomposite thin films is important for modifying them for device purposes. One structure that has gained a lot of attention is vertically aligned nanocomposites (VANs) due to the increased vertical coupling between two or more phases of materials and the unique nanostructures achievable through controlling deposition factors. </p> <p>VAN thin film growth involves many factors: diffusion, substrate surface conditions, source material composition, and deposition temperature and rate. The two main approaches to thin film fabrication are bottom-up and top-down. Bottom-up growth focuses on the self-assembly of the nanostructure. This work focuses on the self-assembly of VAN thin film materials through controlling the thermodynamic and kinetic factors involved in thin film growth. The main factors being considered in this work are substrate manipulation, oxygen gas flow during deposition, deposition rate, and composition. The effectiveness of each of these methods is evaluated in comparison to each other and their growth of VAN thin film materials along with the future work needed to refine each nanostructure manipulation method. </p>

This research focuses on experimental investigations of the drying and bending properties of wood flakes. Three species (southern yellow pine, sweetgum, and yellow-poplar) were tested. Experiments on flake drying and effect of flake properties (cutting direction and dimension) and an external factor (temperature) were used to evaluate the flake drying process. Drying experiments were conducted using a convection oven. Bending properties of dried flakes were also measured. Modulus of elasticity (MOE), modulus of rupture (MOR), and strength at proportional limit (SPL) of flakes were measured based on Methods of Testing Small Clear Specimens of Timber (ASTM D143-94) using a miniature material tester. The drying curve was characterized by a second-order/quadratic equation. This equation was then differentiated to get the drying rate curve. Observation on drying and drying rate curves revealed that the rate of moisture loss consists of two falling rate periods; no constant rate drying period was observed. First falling rate drying period is controlled by convective heat transfer. Bound water diffusion controls the second falling rate drying period. Species, cutting direction, dimension, and temperature were found to have significant effect on drying rate of wood flakes. Southern yellow pine has the fastest drying rate followed by sweetgum then yellow-poplar. Differences in drying rate between species were attributed to differences in specific gravity and other factors. Radially-cut specimens have a slower drying rate than tangentially-cut specimens. There were also significant differences in drying rate between the four different flake dimensions. Thickness was found to be the more sensitive parameter in terms of dimensions. As expected, drying temperature also had highly significant effect on drying rate. An increasing trend in drying rate was observed as drying temperature increased. Simulation of flake drying using a numerical model yielded a different result. Simulated flake drying has two drying periods: a constant rate and falling rate. Moisture of the flake decreases constantly and surface temperature increases rapidly to boiling point and remains there in the constant rate drying period. During the falling rate period, rate of moisture transport is limited by the ability of water to diffuse through wood and flake temperature starts to rise. Bending properties were found to vary between and within the three species. Southern yellow pine had the lowest bending stiffness and strength followed by sweetgum while yellow-poplar had the highest bending properties. Radially-cut specimens were found to have lower MOE, MOR, and SPL than tangentially-cut specimens. Drying temperature was also found to have a significant effect on bending stiffness and strength. A decreasing trend in bending properties was observed when drying temperature was increased. / Ph. D.

Polymer applications have become more demanding as industry continuously turns to more microscopic parts. Due to the interactions of the polymer chains with the supporting surface and the air interface, the thinner films required for such applications have distinctly different properties than those of the well-defined bulk systems. The goal of the current research is to elucidate the behavior of ultrathin films. Two separate studies were performed on thin films supported on silicon wafer substrates: the first focuses on the viscoelastic cooperativity of thin films, and the second concentrates on the morphological behavior of polymer brush films. For the first study, polymethyl methacrylate films were spin coated onto silicon wafers, and the film thickness was determined using ellipsometry. A series of thin films were examined using techniques such as dielectric analysis and thermal mechanical analysis. The theory of cooperativity, which explains polymeric behavior using the intermolecular and intramolecular forces among polymer chains, was employed to understand the behavior of these thin films. Another type of thin film, a polymer brush, was investigated in the second study. Polymer brushes are formed by chemically bonding one end of many polymer chains to a substrate. The other ends of the chains can interact with the surrounding environment creating a brush-like structure. Constraining one end of a polymer chain alters the behavior of such a thin film. Polymer brushes of the di-block copolymer poly(t-butyl methacrylate) and polystyrene were produced on silicon wafers using spin coating techniques. The effects of both grafting density and solvent washes were analyzed using contact angle analysis and atomic force microscopy. In addition, hydrolysis was successfully performed on existing polymer brush samples to produce polymer brushes of the di-block copolymer polymethyl acrylic acid and polystyrene. / Master of Science

Electro-optical properties of thin film are of great interest owing to the perpetual demand for miniaturization and higher speed devices for communication, electronic, and biomedical applications. The thickness of polymer films developed for these applications has decreased dramatically making interfacial effects significant. It is well documented that, in submicron thickness range, both film/substrate & film/air interface are critical. In this study, we probe the dynamics of electro-optical polymer thin films in the sub-micron thickness regime to understand interfacial effects. The polymer chain dynamics of Polypropylene oxide (PPO) under electric field are investigated in this study. The effects of electric field strength, frequency, and polymer molecular weight on the polymer chain dynamics under electric field are studied. Experimental results show that PPO exhibits both piezoelectric and electrorestrictive effects at significantly high frequencies (101kHz range). Conventional organic materials are responsive only at frequencies in <1kHz range. A high signal-to-noise ratio differential interferometry is designed to quantitatively study the effects of film thickness, electric field frequency and amplitude on the dynamic properties of PPO thin films ranging from 30 nm to 400 nm. The interferometer can concurrently monitor the index of refraction, thickness change of polymer films, and birefringence due to the applied electrical field. / Master of Science

No description available.

No description available.

Graduation date: 2006 / A discrete trap model is developed and employed for elucidation of thin-film transistor (TFT) device physics trends. An attractive feature of this model is that only two model parameters are required, the trap energy depth, E[subscript T], and the trap density, N[subscript T]. The most relevant trends occur when E[subscript T] is above the Fermi level. For this case drain current – drain voltage simulations indicate that the drain current decreases with an increase in N[subscript T] and E[subscript T]. The threshold voltage, V[subscript T], extracted from drain current – gate voltage (I[subscript D] – V[[subscript GS]) simulations, is found to be composed of two parts, V[subscript TRAP], the voltage required to fill all the traps and V[subscript ELECTRON], the voltage associated with electrons populating the conduction band. V[subscript T] moves toward a more positive voltage as N[subscript T] and E[subscript T] increase. The inverse subthreshold voltage swing, S, extracted from a log(I[subscript D]) – V[subscript GS] curve, increases as N[subscript T] and E[subscript T] increase. Finally, incremental mobility and average mobility versus gate voltage simulations indicate that the channel mobility decreases with increasing N[subscript T] and E[subscript T].

Thesis (M.S.)--Rochester Institute of Technology, 1989. / "References": leaves 20-23.

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 119-133). Also available on the World Wide Web.